[amdgpu] 4700U suspend issue and warning at dc_link_set_backlight_level

Sometimes my Renoir-based laptop freezes (black screen) on resume and I have to use sysrq. Whether resuming is successful or not, I always see an amdgpu bug in my dmesg, starting with a WARNING in drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link.c:2545 dc_link_set_backlight_level+0x8a/0xf0

My config: Arch Linux kernel 5.8.0 with Gnome Shell. Hardware: Lenovo IdeaPad 5 14" 14ARE05 81YM (latest bios).